Adjustable chain wheel and components thereof

Abstract: A tooth wheel (33) intended to co-act with a transmission member with transmission elements (19,20), which tooth wheel (33) bears a number of protrusions (34) arranged on the periphery which are each provided with at least one contact surface (26,27) for co-action with the transmission elements (19,20), comprising self-adjusting adjusting means for adjusting the pitch of the contact surfaces (26,27), wherein each protrusion (34) can swivel substantially in the main plane of the tooth wheel (33) round at least one centre (36,37) outside the connecting line between the centre line of the tooth wheel (33) and the zone of engagement between the contact surface (26,27) and a transmission element (19,20). It is an object of the invention to embody a tooth wheel (33) such that the distribution of the forces over the protrusions (34) is better in the case of individual variations of the relevant pitch distances. With a view to this object the tooth wheel (33) according to the invention has the feature that during a swivelling of the relevant protrusion (34) the contact surface (26,27) of the transmission element (19,20) co-acting therewith undergoes a substantial radial displacement in relation to the tooth wheel (33).

Description: The invention relates to a device having a toothed wheel to co-act with a transmission member with transmission elements, for instance a chain with links or a toothed belt as defined in the preamble of claim 1 and 2 respectively which is known from US-A 1 633 746. A similar device is known from DE-C 165 920 in which the toothed wheel comprises a separate carrier which bears a number of protrusions arranged on the periphery, which protrusions are each provided with one contact surface for co-action with the transmission elements, comprising self-adjusting adjusting means for adjusting the pitch of the contact surfaces, wherein each protrusion can swivel substantially in the main plane of the tooth wheel round at least one centre outside the connecting line between the centre line of the tooth wheel and the zone of engagement between the contact surface and a transmission element. In relation to this prior art it is an object of the invention to embody a self-adjusting tooth wheel such that the distribution of the forces over the protrusions is better in the case of individual variations of the relevant pitch distances. With a view to this object the device according to the invention has the features as defined in claim 1 and 2 respectively. Preferred embodiments including also toothed wheels and protrusions forming part of the toothed wheels are defined in the appended claims. In order to be certain that the protrusions are situated in the suitable position prior to engagement with the transmission elements, use can advantageously be made of resetting spring means which urge the contact surfaces to an extreme rest position. It is noted that the dimensioning of the device must be such that at the beginning of the engagement with the transmission elements the contact surfaces can indeed come into contact with these elements. The use of resetting spring means can be dispensed with under particular conditions, for instance in the case where, in the free, i.e. non-loaded situation of the protrusions, the latter are situated on the underside of a vertically disposed tooth wheel. It must then be ensured however that the force of gravity is sufficient to tilt the protrusions to the desired position while overcoming the associated friction forces. The invention also relates to a toothed wheel and a protrusion intended to serve as component of a device as specified above. This protrusion and toothed wheel is characterized by the features of claims 6 to 9. The invention will now be elucidated with reference to the annexed drawing. In the drawing: figure 1 shows a schematic view of an adjustable tooth wheel not constructed in accordance with the invention; figure 2 is a schematic view in which is shown the manner in which the interaction of forces between the tooth wheel according to the invention and the chain according to figure 5 takes place; figure 3 shows an embodiment of the invention in partly broken away perspective view; figure 4 shows the cross section V-V according to figure 2; and figure 5 shows a side view of a further embodiment, which is given preference. Figure 1 shows a tooth wheel not constructed according to the invention. The tooth wheel 13 according to figure 3 bears a number of protrusions 14 which are pivotable on pivot shafts 15. These protrusions each bear two concave contact surfaces designated respectively with 16 and 17. An adjustable stop in the form of an adjusting bolt 18 is added to each protrusion 14 and limits the inward stroke of the relevant protrusion. In this manner the adjusting of each bolt can take place on the basis of the effective pitch of the corresponding pivot shafts 19 and its contact surfaces 19' such that the contact surfaces 16 have the same mutual pitch distance as the pivot shafts 19. The rotation direction is designated with an arrow 40. As is shown clearly in figure 1, pivot shafts 19 co-act with the leading contact surfaces 16, while pivot shafts 20 co-act with the trailing contact surfaces 17. As can further be seen clearly in figure 1, the contact surfaces 16, 17 each have a form such that the positions of the pivot shafts 19, 20 in relation to the contact surfaces 16, 17 co-acting therewith are not fixed but permit a certain play. Figure 2 shows the manner in which by means of spring means (not shown) the tooth wheel according to figure 1 can be modified to obtain a self-adjusting tooth wheel according to the invention. The tooth wheel 21 has substantially the same structure as tooth wheel 13 according to figure 1. Corresponding elements are therefore designated here with the same reference numerals as in figure 1. Tooth wheel 21 is driven by a moment of force M and thus drives the chain 6 by means of contact surfaces 16. The protrusions 14 are urged outward by means of spring means (not shown). In the position furthest to the left in figure 2, in which a link has come into contact with a protrusion 14, the preceding link has already pivoted in relation to the associated link. The tensile force in the chain can of course only intersect the line between the axes of the pivot shafts 19, 20. Should the relevant forces be resolved, they must then extend through the pivot shafts 15 for a mechanically stable situation. This self-adjusting action is obtained automatically because a resultant force which does not extend through a pivot shaft 15 results immediately in an associated displacement of the relevant protrusion 14, whereby the stable situation is obtained. Only at the moment when this condition of mechanical stability is fulfilled is a protrusion at rest. Figures 3 and 4 show a tooth wheel 22 which comprises two flanges 23, 24, between which symmetrical protrusions 25 are guided slidably. The protrusions 25 each have a leading concave contact surface 26 and a trailing concave contact surface 27. Each protrusion has two slotted holes, respectively a leading slotted hole 28 and a trailing slotted hole 29. Co-acting with the slotted holes are the respective guide pins 30, 31 which are connected to the flanges 23, 24. A resetting spring 32 urges each protrusion 25 into the active position shown on the left in which the protrusion 25 is pivotable round the guide pin 31. A power exchange with a relevant link of a chain (not drawn) can herein be transmitted by means of contact surface 26. Essential, as in the embodiment according to figure 2, is that this embodiment is self-adjusting due to the ability to pivot round the pin 31. The protrusions 25 are detachable, as is particularly clear with reference to figure 4. It is therefore pointed out emphatically that the invention also relates to separate components, in particular the protrusions 25 and the disc consisting of the flanges 23, 24. The guide pins 30, 31 form first fixing means which are present on the disc 23, 24 and which together with the slotted holes 28, 29 in the protrusions 25 support these protrusions 25 detachably. Figure 5 shows a tooth wheel 33 bearing slidably guided protrusions 34 which are each provided with two slotted holes 35, 36 which co-act with guide pins 37, 38 respectively. Slotted holes 35 and 36 are placed concentrically of the pins 38 and 37 respectively. As the figure shows, a first engagement of a link takes place by co-action of the leading contact surface 26 of a protrusion 34 with the pivot shaft 19 and its contact surface 19'. The protrusion 34 placed furthest to the left in figure 5 shows this situation. Pivoting takes place on the trailing pivot pin 38. In the top position in figure 5 the protrusion 34 rests with the ends of the slotted holes 35, 36 against the guide pins 37, 38. A pivoting then takes place round the leading guide pin 37. Resetting springs 39 urge the protrusions 34 to the shown extreme position. As shown in figure 5, contact with the shafts 19, 20 and its contact surfaces 19', 20' can take place with certainty in this extreme position. It is noted that use of the resetting springs 39 could in principle be dispensed with in the case where tooth wheel 33 is disposed vertically, the chain extends over the upper portion thereof and the force of gravity is sufficient to tilt the protrusions 34 in the bottom left quadrant to the position indicated there. If desired use could also be made of cam means (not drawn) which in the said quadrant urge the protrusions 34 to the desired start position. After the elucidation given above with reference to figure 2 it will be apparent that tooth wheel 33 is self-adjusting and inherently stable. The tooth wheel according to figure 2 has a technical drawback. On the output side of the tooth wheel, thus in the zone where the chain leaves the tooth wheel, the situation can occur, in the case of a very great stretch in the chain, in which the outermost teeth always absorb the greater part of the forces for transmitting. It will be apparent that this concentration of force can result in undesired wear. The embodiments of figures 3, 4 and 5 do not have this drawback. A considerably better distribution of forces over the teeth takes place with these tooth wheels. This results in reduced wear and an increased effective lifespan. Attention is further drawn to the fact that the embodiments of figures 3, 4 and 5 could be simplified further by making each tooth swivellable, not round two centre lines located at a mutual distance, but round only one centre line. A tooth according to figure 3 can then for instance be pivotable round only one pivot axis which extends through the central zone of the tooth.

Claims: Device having a toothed wheel (21) co-acting with a transmission member with transmission elements, for instance a chain with links or a toothed belt, said toothed wheel (21) swivellingly bears a number of protrusions (14) arranged on its periphery, each protrusion (14) is provided with a contact surface (16) co-acting with a contact surface (19') of a respective transmission element (19), said device comprises self-adjusting adjusting means to adjust the pitch of the contact surfaces (16), characterised in that each protrusion (14) is arranged to swivel substantially in the main plane of the toothed wheel (21) round the centre outside the connecting line between the centre of the toothed wheel and the zone of engagement between the contact surface (16) of said protrusion (14) and the contact surface (19') of said transmission element, whereby during a swivelling of the relevant protrusion (14) the contact surface (19') of the transmission element (19) co-acting therewith undergoes a substantial radial displacement in relation to the toothed wheel (21). Device having a toothed wheel (33) co-acting with a transmission member with transmission elements (19, 20), for instance a chain with links or a toothed belt, said toothed wheel (33) swivellingly bears a number of protrusions (34) arranged on its periphery, said device comprises self-adjusting adjusting means to adjust the pitch of contact surfaces provided on said protrusion and a respective transmission element (19, 20), characterised in that each protrusion (34) is provided with two contact surfaces (26, 27) co-acting with a contact surface (19', 20') of a respective transmission element (19, 20), wherein each protrusion (34) is arranged to swivel substantially in the main plane of the toothed wheel (33) round at least one centre outside the connecting line between the centre of the toothed wheel and the zone of engagement between at least one contact surface (26, 27) of said protrusion and one contact surface (19', 20') of said transmission element, whereby during a swivelling of the relevant protrusion (34) the contact surface (19', 20') of the transmission element (19, 20) co-acting therewith undergoes a substantial radial displacement in relation to the toothed wheel (33). Device as claimed in claim 1 or 2, wherein the adjusting means comprise spring means. Device as claimed in claim 2, wherein each protrusion is guided slidably by two co-acting guide pins and slotted holes forming part of the tooth wheel and the protrusions, which slotted holes have a form such that the protrusion can undergo an angular displacement, wherein in the one extreme angular position the protrusion is pivotable round the one pin and in the other extreme angular position the protrusion is pivotable round the other pin. Device as claimed in any one of the preceding claims, wherein resetting spring means are provided which urge the contact surfaces to an extreme rest position. Toothed wheel (21) swivingly bearing a number of protrusions (14) arranged on its periphery on mutually equal angular distances, each protrusion (14) being provided with a concave contact surface (16) and being arranged to swivel substantially in the main plane of the toothed wheel (21) round a centre (15) characterized in that the centre (15) and the contact surface (16) are positioned on different angular positions relative to the centre of the toothed wheel (21). Protrusion (14) forming part of the toothed wheel (21) according to claim 6 and comprised of a generally block-shaped structure provided in one corner zone with swivel means (15) determining a centre of swivelling and a concave outer contact surface (16) arranged on a distance relative thereto characterized in that the concave outer contact surface (16) is arranged in the diagonally opposed corner zone. Toothed wheel (33) swivingly bearing a number of protrusions (34) arranged on its periphery on mutually equal angular distances, each protrusion (34) being provided with a concave contact surface (26) and being arranged to swivel substantially in the main plane of the toothed wheel round a centre characterized in that each protrusion is arranged to swivel round either one of two centres (38, 37); each protrusion (34) is provided with a second concave contact surface (27); and each centre (38, 37) is associated with a respective contact surface (26, 27), the connecting lines between the two centres (38, 37) and the respective contact surfaces (26, 27) extending in intersecting relation. Protrusion (34) forming part of the toothed wheel (33) according to claim 6 and comprised of a generally block-shaped structure provided in one corner zone with swivel means determining a centre of swivelling and a concave outer surface (26) arranged on a distance relative thereto characterized in that the protrusion (34) is provided in a second corner zone adjacent to said first corner zone with second swivel means (37) determining a second centre of swiveling; and the protrusion is provided with a second concave outer surface (27) arranged in the second corner zone diagonally opposed thereto.

Inventors: KORENBERG HENDRIK JAN, ROTH ARJEN ROBERT, TIGGELOVEN LEONARDUS JOZEPHUS, KORENBERG, HENDRIK JAN, ROTH, ARJEN ROBERT, TIGGELOVEN, LEONARDUS JOZEPHUS ANTONIUS
Applicants: STORK RMS BV, STORK R.M.S. B.V.
Application year: 1994
Main classification: F16H55
IPC codes: F16H55